Sheathed electric cable



Patented Oct. 21, 1941 SHEATHED ELECTRIC CABLE Helmut Ziindorf, Rodenklrchen-on-the-Rhine, Germany Application December c. 1938, Serial No. 244,155 In Germany December 7, 193'! 4 Claims.

The invention relates to an electric cable without a lead jacket and with a metallic watertight flexible cable jacket or casing, and to a process for the production of such cable casings as flexible metallic hose or pipe. The familiar production of flexible metallic hose from helically coiled strip, or from a plurality of adjacently disposed coiled strips, is effected in such wise that the contacting edges of the strip or strips are tightly or loosely folded or rabbeted together. The manufacturing processes that up to the present time have been usual for' this purpose can not however be made use of for encasing objects with a metallic jacket tightly covering them. The production of ordinary flexible metallic hwe that is used for conveying fluids or gases namely assumes the possibility of providing during production a winding mandrel that is capable of offering resistance and that does not yield. During the production of flexible metallic hose the metal strips are wound round this mandrel and the adjacent windings are then united with one another, whereby the winding mandrel serves as a.

counter-support and takes the radially acting pressure of the folding tool during the squeezing together of the contacting strip edges. For this reason flexible metallic hose could not up to the present time be made use of in cases in which the hose had to lie tightly against a core housed inside it. It is possible to use a hollow mandrel; this however has the drawback that intermediate spaces are produced between the insulation and. the cable casing.

The customary methods of manufacturing flexible metallic hose from strips that are folded together at their edges can consequently not be used, without further provisions, for encasing the insulation of an electric cable. It is however not possible to fold together by strong pressure the hose coils that contact one another unless a winding mandrel is used, because the cable insulation does not stand up.

In accordance with the present invention the production of hose jackets for electric cables has been made possible by creating a substitute for the winding mandrel, in that there is first brought on to the cable insulation an envelope that itself lies tightly against the insulation and that takes an external pressure, which preferably acts radially, and distributes it over a larger area of the insulation. This envelope, which is capable of offering resistance, is preferably made of metal, for example of a self-supporting cable formation of round or shaped wires that engage into one another with tongues and grooves. Instead of this, a fiat strip (or a pluralityof flat strips of steel or aluminum for example), in tight contact with the adjacent edges abutting or overlapping. may be wound on smoothly, so that a mechanically rigid, smooth core is produced. After this a watertight metal hose is produced round this core by winding on it a flat strip (or a plurality of strips) of zinc-coated metal (iron or soft aluminum for example), whereby the core that has wrapped round it a flat strip, for example of steel, aluminum, or a magnesium alloy, serves as an unyielding counter-support, equivalent to a winding mandrel that is, so that the metal strip that is wound on it in the same or the opposite direction into a tight hose may have its edges folded together in a way similar to that occurring in the manufacture of flexible metallic hose, without the cable insulation hereby yielding or deforming under the action of the pressure occurring. The strip holder and folding tool hereby rotate about the cable core that moves onward in an axial direction. Such a core is of sufilcient strength and rigidity for the folded strip edges to be Joined together perfectly without damaging the insulation. The fold grooves of the metal hose may moreover be packed or made tight by interposed metallic or organic strips or threads. Strips made used for metallic packing strips; threads of jute, tarred hemp, or artificial materials may be used for organic threads. When steel is used for the flat strip winding that serves as a counter-support. the flat steel strip may before it is wound on be given a greater curvature, by being guided over bending rolls, wheels, or pins, than corresponds to the diameter of the cable insulation, so that the strip rests against the cable insulation with a clamping action in order that it may lie tightly against it.

The invention is illustrated in the accompanying drawing wherein:

Fig. 1 is a side elevation, partly broken away and in section, of a cable construction embodying the invention; and

Fig. 2 is a fragmentary view showing a modifled construction.

In Flg. 1 of the drawing there is shown a metallic conductor ll provided with insulation ll. Over this there may be placed a water and oil impervious layer I2 composed, for example, of cellulose ester or polystyrol. Then there is applied a wrap of coiled metal tape I: which is sufllciently resistant to take considerable radial pressure. And over this there is disposed the coiled metal hose I 4 provided with pressure of lead may be formed folds l5. As stated, packing (not shown may be incorporated in the folds.

. In Fig. 2 the metal tape I3 which is placed over the impervious layer l2 and the insulation II' is provided with a tongue and groove engagement instead of an overlapping engagement, as shown in Fig. 1. Over this tape the coiled and sealed metal hose I4 is placed as in the first form.

'While certain embodiments have been specifically described, it will be obvious that the gagement with the said wrapp n adjacent ed s of the metal coils being folded together unde pressure to provide a watertight joint.

2. An electric cable as set forth in the preceding claim in which the folded edges of the metal coils have interposed packing strips.

3. An electric cable having a flexible, watertight envelope comprising, in combination, an insulated conductor, a self-supporting metal wrapping over and upon the conductor insulation. said self-supporting wrapping being capable of resisting externally applied mechanical pressure, and a coiled metal hose disposed over and in close engagement with the said wrapping, ad-- jacent edges of the metal coils being folded together under pressure to provide a watertight joint.

4. An electric cable as set forth in claim 3 in which the self-supporting wrapping comprises shaped wires having tongue and groove engagement at their adjacent edges.

HELMUT ziiNDoRF. 

